Instrumentation amplifier combines low noise, power and distortion for precision signal detection in industrial applications

June 22, 2011 // By Paul Buckley
Analog Devices, Inc., has introduced an ultra-low noise, low-power low-distortion instrumentation amplifier (in amp) for the precision measurement of small signals present in noisy industrial operating environments. The new high-bandwidth AD8429 in amp claims to be one of the fastest in amps on the market with a current feedback architecture that offers 15 MHz (G=1) bandwidth and a 22-V/μs slew rate, which is 30 percent higher than competing in amps.

With a low distortion of -130 dB, the AD8429 is robust enough for applications that demand reduced size, power and distortion levels, such as healthcare instrumentation, precision data acquisition equipment and industrial vibration analysis.     

With 1-nV/√Hz input noise and 45-nV/√Hz output noise, the AD8429 operates across the extended industrial temperature range of -40 to 125˚C. Input bias current of 50-nA is orders of magnitude lower than the 12,000-nA bias current of other in amps, while the 100-μV input offset voltage of the AD8429 is two to three times lower.      

The AD8429 has a 90-dB CMRR (common-mode rejection ratio) when operating in dc mode and an 80-dB CMRR in ac mode, which prevents unwanted signals from corrupting smaller signal acquisition. The CMRR increases with the gain to provide high signal rejection when it is needed most, and ADI's high-performance pin configuration allows the AD8429 to reliably maintain high CMRR at frequencies well beyond those of typical instrumentation amplifiers. This high-level of precision performance is available in a 4-mm x 5-mm, JEDEC compliant, plastic SOIC_N (small outline package, narrow body) package.     

The AD8429 provides analog design engineers with a versatile, flexible in amp featuring a ±4-V to ±18-V dual power supply.  Gain is set from 1 to 10,000 with a single resistor, and a reference pin allows the user to offset the output voltage. The feature can be useful to shift the output level when interfacing to a single-supply signal chain.

The AD8429 packaged in an 8-lead SOIC is in full volume production now and is priced at $3.50 each per 1,000.     

More information about the AD8429 instrumentation amplifier at